Enhanced electrochemical performance of solution impregnated La0.8Sr0.2Co0.8Ni0.2O3−δ cathode for intermediate temperature solid oxide fuel cells

Solution impregnated La_0.8Sr_0.2Co_0.8Ni_0.2O₃ + Gd-doped CeO₂ (LSCN + GDC) cathodes for intermediate temperature solid oxide fuel cells (IT-SOFC) are prepared and their electrochemical properties are evaluated and compared with the conventional LSCN cathodes. The results indicate that the cathode performance can be enhanced by the presence of the nanosized microstructure produced with the solution impregnation method. It is determined that the amount of LSCN loading in the LSCN + GDC composite cathode needs to be higher than 35 wt% in order to achieve a performance superior to that of the conventional LSCN cathode. The optimum amount of LSCN loading is in the range of 45-55 wt% with an activation energy near 1.32 eV for oxygen reduction. At temperatures between 600 and 750 °C, the polarization resistance of the 55 wt% LSCN loaded LSCN + GDC cathode is in the range of 1.07 and 0.08 Ω cm², which is only about one half of that for the conventional cathode.     

La0.99Co0.4Ni0.6O3−δ-Ce0.8Gd0.2O1.95 as composite cathode for solid oxide fuel cells

We have studied a new composite SOFC cathode consisting of LaCo_0.4Ni_0.6O_3−δ (LCN60) and Ce_0.9Gd_0.1O_1.95 (CGO). The polarisation resistance (R_P) at 750 °C and OCV was measured to 0.05 ± 0.01 Ω cm² and the activation energy was determined to be about 1 eV. The impedance spectra were modelled with an EQC model consisting of a high frequency Z_RQ circuit and a medium frequency Gerischer impedance, Z_G. The resistance of Z_G was found to decrease with approximately a factor of two as a consequence of infiltration of (La_0.6Sr_0.4)_0.99CoO₃ into the porous LCN60-CGO structure. R_P of both infiltrated and non-infiltrated LCN60-CGO cathodes is substantially lower than that of LSM-YSZ and comparable with single phase LSC cathodes at low T due to its low E_A. R_P was also found to be stable at 750 °C and OCV. The cathodes were integrated onto ScYSZ based anode supported cells which were measured to have an ASR of 0.16-0.18 Ω cm² at 750 °C.     

High performance proton-conducting solid oxide fuel cells with a stable Sm0.5Sr0.5Co3−δ-Ce0.8Sm0.2O2−δ composite cathode

A Sm_0.5Sr_0.5CoO_3−δ-Ce_0.8Sm_0.2O_2−δ (SSC-SDC) composite is employed as a cathode for proton-conducting solid oxide fuel cells (H-SOFCs). BaZr_0.1Ce_0.7Y_0.2O_3−δ (BZCY) is used as the electrolyte, and the system exhibits a relatively high performance. An extremely low electrode polarization resistance of 0.066 Ω cm² is achieved at 700 °C. The maximum power densities are: 665, 504, 344, 214, and 118 mW cm⁻² at 700, 650, 600, 550, and 500 °C, respectively. Moreover, the SSC-SDC cathode shows an essentially stable performance for 25 h at 600 °C with a constant output voltage of 0.5 V. This excellent performance implies that SSC-SDC, which is a typical cathode material for SOFCs based on oxide ionic conductor, is also a promising alternative cathode for H-SOFCs.     

A cobalt-free Sm0.5Sr0.5Fe0.8Cu0.2O3−δ-Ce0.8Sm0.2O2−δ composite cathode for proton-conducting solid oxide fuel cells

A cobalt-free composite Sm_0.5Sr_0.5Fe_0.8Cu_0.2O_3−δ-Ce_0.8Sm_0.2O_2−δ (SSFCu-SDC) is investigated as a cathode for proton-conducting solid oxide fuel cells (H-SOFCs) in intermediate temperature range, with BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3−δ (BZCYYb) as the electrolyte. The XRD results show that SSFCu is chemically compatible with SDC at temperatures up to 1100 °C. The quad-layer single cells of NiO-BZCYYb/NiO-BZCYYb/BZCYYb/SSFCu-SDC are operated from 500 to 700 °C with humidified hydrogen (∼3% H₂O) as fuel and the static air as oxidant. It shows an excellent power density of 505 mW cm⁻² at 700 °C. Moreover, a low electrode polarization resistance of 0.138 Ω cm² is achieved at 700 °C. Preliminary results demonstrate that the cobalt-free SSFCu-SDC composite is a promising cathode material for H-SOFCs.     

Characteristics of Ba0.5Sr0.5Co0.8Fe0.2O3−δ–La0.9Sr0.1Ga0.8Mg0.2O3−δ composite cathode for solid oxide fuel cell

Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ–La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ composite cathodes are prepared successfully using combustion synthesis method. Microstructure, chemical compatibility and electrochemical performance have been investigated and analyzed in detail. SEM micrographs show that a structure with porosity and well-necked particles forms after sintering at 1000 °C in the composites. Grain growth is suppressed by addition of La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ phase and grain sizes decrease with increasing weight percent of La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ phase in the composites. Phase analysis demonstrates that chemical compatibility between Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ and La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ is excellent when the weight percent of La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ in the composite is not more than 40%. Through fitting ac impedance spectra, it is found that the ohmic resistance and polarization resistance decrease with increasing La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ content. The polarization resistance reaches a minimum at about 30 and 40 wt.% La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ in the composite.     

Thermochemical compatibility and polarization behaviors of La0.8Sr0.2Co0.8Ni0.2O3−δ as a cathode material for solid oxide fuel cell

Thermochemical compatibilities with Ce_0.8Gd_0.2O_2−δ (GDC) electrolyte and electrochemical behaviors under the condition of anodic or cathodic current treatment are investigated for La_0.8Sr_0.2Co_0.8Ni_0.2O_3−δ (LSCN) cathode of solid oxide fuel cell (SOFC). X-ray diffractometer (XRD) shows that cation exchange at 1150 °C leads to the formation of solid state solution between the cathode and electrolyte. Considering thermal expansion coefficient (TEC) and conductivity, La_1−xSr_xCo_1−yNi_yO_3−δ with the composition of La_0.8Sr_0.2Co_0.8Ni_0.2O_3−δ is indicated as a promising cathode for intermediate temperature SOFC. Electrochemical measurement reveals that the performance of LSCN cathode shows reversibility under anodic with subsequent cathodic current treatment. Further, the low frequency electrode process is strongly affected by anodic current. While the high frequency arc shows independent relationship with current polarization.     

In situ sinterable cathode with nanocrystalline La0.6Sr0.4Co0.2Fe0.8O3−δ for solid oxide fuel cells

A nanocrystalline powder with a lanthanum based iron- and cobalt-containing perovskite, La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ (LSCF), is investigated for solid oxide fuel cell (SOFC) applications at a relatively low operating temperature (600-800 °C). A LSCF powder with a high surface area of 88 m² g⁻¹, which is synthesized via a complex method with using inorganic nano dispersants, is printed onto an anode supported cell as a cathode electrode. A LSCF cathode without a sintering process (in situ sintered cathode) is characterized and compared with that of a sintering process at 780 °C (ex situ sintered cathode). The in situ sintered SOFC shows 0.51 A cm⁻² at 0.9 V and 730 °C, which is comparable with that of the ex situ sintered SOFC. The conventional process for SOFCs, the ex situ sintered SOFC, including a heat treatment process after printing the cathodes, is time consuming and costly. The in situ sinterable nanocrystalline LSCF cathode may be effective for making the process simple and cost effective.     

Electrospinning La0.8Sr0.2Co0.2Fe0.8O3−δ tubes impregnated with Ce0.8Gd0.2O1.9 nanoparticles for an intermediate temperature solid oxide fuel cell cathode

In order to reduce the polarization resistance of the cathode, we have developed one-dimensional (1D) nanostructured La_0.8Sr_0.2Co_0.2Fe_0.8O_3−δ (LSCF) tubes/Ce_0.8Gd_0.2O_1.9 (GDC) nanoparticles composite cathodes for solid oxide fuel cell. Uniform LSCF/PVP composite nanofibers have been firstly synthesized by a single-nozzle electrospinning technique, followed by firing at 800 °C for 2 h to form one-dimensional LSCF tubes. Subsequently, the GDC phases were introduced into tube structured LSCF scaffold pre-sintered on a GDC pellet by a multi-impregnation process. Electrochemical Impedance spectra reveal that nanostructured LSCF tubes/GDC nanoparticles composite cathodes have a better electrochemical performance, achieving area-specific resistances of 4.70, 1.12, 0.27 and 0.07 Ω cm² at 500, 550, 600 and 650 °C for the composite of GDC and LSCF in a weight ratio of 0.52:1. The low ASR values are mainly related to its optimal microstructure with larger triple-phase boundaries and higher porosity. These results suggest that LSCF tube/GDC nanoparticle composite can be an alternative cathode material for intermediate temperature solid oxide fuel cell (IT-SOFC).     

Fabrication and evaluation of the electrochemical performance of the anode-supported solid oxide fuel cell with the composite cathode of La0.8Sr0.2MnO3−δ-Gadolinia-doped ceria oxide/La0.8Sr0.2MnO3−δ

The anode-supported single cell was constructed with porous Ni-Yittria-stabilized zirconia (YSZ) as the anode substrate, an airtight YSZ as the electrolyte, and a screen-printed La_0.8Sr_0.2MnO_3−δ (LSM)-Gadolinia-doped ceria (GDC)/LSM double-layer cathode. The SEM results show that the YSZ thin film is highly integrated, fully dense with a thickness of 13 μm, and exhibits excellent compatibility between cathode and electrolyte layers. The effects of feed rates of the reactants, temperature, and contact pressure between the current collector and the unit cell were systematically investigated. The results are based on the assumption that the anode contribution to the polarization resistance is negligible. Our analysis showed that the electrochemical reaction is limited by mass transfer control when the airflow rate is decreased to 500 ml min⁻¹. The maximum power density is 204.6 mW cm⁻² at 800 °C with H₂ and air at flow rates of 800 and 2000 ml min⁻¹, respectively. According to the AC-impedance data, the resistances of charge transfer at the electrode/electrolyte interface are 3.79 and 1.90 Ω cm². The resistances of oxygen-reduction processes are 3.63 and 1.01 Ω cm² at 700 and 800 °C, respectively. The results from the sensitivity analysis of the variation of contact pressure between current collectors and membrane electrode assembly (MEA) show that the influence is enhanced at the regions of the high current density.     

Characterization of nanosized Ce0.8Sm0.2O1.9-infiltrated Sm0.5Sr0.5Co0.8Cu0.2O3−δ cathodes for solid oxide fuel cells

This study investigates the microstructure and electrochemical properties of Sm_0.5Sr_0.5Co_0.8Cu_0.2O_3−δ (SSC-Cu) cathode infiltrated with Ce_0.8Sm_0.2O_1.9 (SDC). The newly formed nanosized electrolyte material on the cathode surface, leading the increase in electrochemical performances is mainly attributed to the creation of electrolyte/cathode phase boundaries, which considerably increases the electrochemical sites for oxygen reduction reaction. Based on the experiment results, the 0.4 M SDC infiltration reveals the lowest cathode polarization resistance (R_P), the cathode polarization resistances (R_p) are 0.117, 0.033, and 0.011 Ω cm² at 650, 750, and 850 °C, and the highest peak power density, are 439, 659, and 532 mW cm⁻² at 600, 700, and 800 °C, respectively. The cathode performance in SOFCs can be significantly improved by infiltrating nanoparticles of SDC into an SSC-Cu porous backbone. This study reveals that the infiltration approach may apply in SOFCs to improve their electrochemical properties.     

Sm0.5Sr0.5Co0.4Ni0.6O3−δ–Sm0.2Ce0.8O1.9 as a potential cathode for intermediate-temperature solid oxide fuel cells

The mixed ionic and electronic conductors (MIECs) of Sm_0.5Sr_0.5Co_0.4Ni_0.6O_3−δ (SSCN)–Sm_0.2Ce_0.8O_1.9 (SDC) were investigated for potential application as a cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFCs) based on an SDC electrolyte. Electrochemical impedance spectroscopy (EIS) technique was performed over the temperature range of 600–850 °C to determine the cathode polarization resistance which is represented by area specific resistance (ASR). To investigate the ORR mechanism, the impedance diagram for 70SSCN–30SDC was measured under applied cathodic voltage from E = 0.0 to E = −0.3 V. It indicated that the charge transfer dominated the rate-determining step at the temperature of 600 °C; whereas the diffusion or dissociative adsorption of oxygen dominated the rate-determining step at the temperature of 800 °C. In this study, the exchange current density (i₀) for oxygen reduction reaction (ORR) was determined from the EIS data. The i₀ value of 70SSCN–30SDC/SDC was 187.6 mA cm⁻² which is larger than the i₀ value of 160 mA cm⁻² for traditional cathode/electrolyte, i.e. LSM/YSZ at 800 °C, indicating that the 70SSCN–30SDC composite cathode with a high catalytically active surface area could provide the oxygen reduction reaction areas not only at the triple-phase boundaries but also in the whole composite cathode.     

Electrochemical performance of La0.7Sr0.3CuO3−δ–Sm0.2Ce0.8O2−δ functional graded composite cathode for intermediate temperature solid oxide fuel cells

The fabrication and electrochemical properties of graded La_0.7Sr_0.3CuO_3−δ–Sm_0.2Ce_0.8O_2−δ (LSCu–SDC) composite cathodes were investigated in this paper. The phase composition, microstructure and electrochemical properties of the electrodes were characterized using X-ray diffraction (XRD), electron microscopy, electrochemical impedance spectroscopy (EIS) and cathodic polarization examinations. The results showed that the triple-layer graded cathode had super electrochemical performance comparing with the monolayer cathode. The graded LSCu–SDC cathode showed a polarization resistance of 0.094 Ωcm², a value much lower than the monolayer LSCu cathode of 0.234 Ωcm² at 800 °C in air. The current density of the graded cathode was 0.341 A cm⁻², more than double higher than monolayer LSCu of 0.146 A cm⁻² at an overpotential of 30 mV. The improved electrochemical performance could be attributed to the improved physical and chemical compatibility of the cathode layers in graded compositions with SDC electrolyte as well as the enlargement of triple-phase boundary for oxygen reduction.     

Preparation and characterization of Ba0.5Sr0.5Fe0.9Ni0.1O3−δ–Sm0.2Ce0.8O1.9 compose cathode for proton-conducting solid oxide fuel cells

A cobalt-free Ba_0.5Sr_0.5Fe_0.9Ni_0.1O_3−δ–Sm_0.2Ce_0.8O_1.9 (BSFN–SDC) composite was employed as a cathode for proton-conducting solid oxide fuel cells (H-SOFCs) using BaZr_0.1Ce_0.7Y_0.2O_3−δ (BZCY) as the electrolyte. The chemical compatibility between BSFN and SDC was evaluated. The XRD results showed that BSFN was chemically compatible with SDC after co-fired at 1100 °C for 5 h. The thermal expansion coefficient (TEC) of BSFN–SDC, which showed a reasonably reduced value (16.08 × 10⁻⁶ K⁻¹), was effectively decreased due to Ce_0.8Sm_0.2O_1.9 (SDC) added. A single cell of Ni–BZCY/Ni–BZCY/BZCY/BSFN–SDC with a 25-μm-thick BZCY electrolyte membrane exhibited excellent power densities as high as 361.8 mW cm⁻² at 700 °C with a low polarization resistance of 0.174 Ω cm². The excellent performance implied that the cobalt-free BSFN–SDC composite was a promising alternative cathode for H-SOFCs.     

Synthesis and characterization of Ba0.5Sr0.5Co0.8Fe0.1Ni0.1O3-δ cathode for intermediate-temperature solid oxide fuel cells

Perovskite Ba_0.5Sr_0.5Co_0.8Fe_0.1Ni_0.1O_3-δ (BSCFNi) oxide is synthesized and characterized as a cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The X-ray diffraction (XRD) spectra show that BSCFNi is chemical compatible with La_0.9Sr_0.1Ga_0.83Mg_0.17O_2.865(LSGM) electrolyte below 950 °C, but weak reaction is observed between BSCFNi cathode and Sm_0.2Ce_0.8O_1.9 (SDC) electrolyte after calcined at 950 °C for 10 h. The XPS results indicate that transition metal cations in BSCFNi sample exist two different valence states, i.e., Co^4+/3+, Fe^4+/3+ and Ni^3+/2+. The average thermal expansion coefficient (TEC) of BSCFNi is 18.7 × 10^?6 K^?1 between 200 °C and 850 °C in air. The maximum electrical conductivity reaches 35.3 Scm^?1 at 425 °C in air. The polarization resistance of BSCFNi cathode on LSGM and SDC electrolytes are 0.033 and 0.066 Ωcm² at 800 °C, respectively. The maximum power density of LSGM electrolyte-supported single cell with BSCFNi cathode reaches 690 mWcm^?2 at 800 °C. These primarily results indicate that BSCFNi is a candidate cathode material for IT-SOFCs.     

High-performance PrBaCo2O5+δ-Ce0.8Sm0.2O1.9 composite cathodes for intermediate temperature solid oxide fuel cell

PrBaCo₂O_5+δ-Ce_0.8Sm_0.2O_1.9 (PBCO-SDC) composite material are prepared and characterized as cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs). The powder X-ray diffraction result proves that there are no obvious reaction between the PBCO and SDC after calcination at 1100 °C for 3 h. AC impedance spectra based on SDC electrolyte measured at intermediate temperatures shows that the addition of SDC to PBCO improved remarkably the electrochemical performance of a PBCO cathode, and that a PBCO-30SDC cathode exhibits the best electrochemical performance in the PBCO-xSDC system. The total interfacial resistances R_p is the smallest when the content of SDC is 30 wt%, where the value is 0.035 Ω cm² at 750 °C, 0.072 Ω cm² at 700 °C, and 0.148 Ω cm² at 650 °C, much lower than the corresponding interfacial resistance for pure PBCO. The maximum power density of an anode-supported single cell with PBCO-30SDC cathode, Ni-SDC anode, and dense thin SDC/LSGM (La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−δ)/SDC tri-layer electrolyte are 364, 521 and 741 mW cm⁻² at 700, 750 and 800 °C, respectively.     

Interaction of La0.8Sr0.2MnO3 interlayer with Gd0.1Ce0.9O1.95 electrolyte membrane and Ba0.5Sr0.5Co0.8Fe0.2O3−δ cathode in low-temperature solid oxide fuel cells

Low-temperature solid oxide fuel cells with a La_0.8Sr_0.2MnO₃ (LSM) interlayer between the Ce_0.9Gd_0.1O_1.95 (GDC) electrolyte membrane (20 μm) and the Ba_0.5Sr_0.5Co_0.8Fe_0.2O₃ (BSCF)–GDC composite cathode are fabricated by sintering the BSCF–GDC composite cathodes at 900, 950 and 1000 °C. The results of scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX) for a model LSM/BSCF bi-layer pellet suggest that Ba, Co and Fe in BSCF as well as La and Mn in LSM have diffused into their counter sides. The X-ray diffraction (XRD) results on the simulated cells also indicate the incorporation of La into the GDC electrolyte membrane and the mutual diffusion of elements between the LSM layer and the BSCF layer. Analysis of the impedance spectra and interfacial reaction activation energies shows that LSM interlayer accelerates the oxygen reduction. Considering a good cell performance and the highest open-circuit voltages (OCVs) at 600–500 °C, the optimum sintering temperature of BSCF–GDC composite cathode onto LSM interlayer is 900 °C.     

La0.8Sr0.2Mn1−xRuxO3−δ as a cathode material for solid oxide fuel cells

Oxides of La_0.8Sr_0.2Mn_1−xRu_xO_3−δ (LSMR) (x = 0, 0.25, 0.50, 0.75, or 1.0) were prepared to fabricate cathodes in solid oxide fuel cells. The crystal structure changed from trigonal (x = 0 or 0.25) to a mixture of trigonal and orthorhombic (x = 0.5) and to orthorhombic (x = 0.75 or 1.0). X-ray photoelectron spectroscopy analysis after electrochemical testing indicated that the relative concentrations of Ru⁴⁺ to Ru⁶⁺ and Mn⁴⁺ to Mn²⁺ influence the performance of a single cell. The transformation from Ru⁴⁺ to Ru⁶⁺ releases two electrons but that from Mn⁴⁺ to Mn²⁺ creates two electron holes (an oxygen vacancy). The relative concentrations in LSMR were determined using the stoichiometric ratio (x) of Ru, and then, the concentrations of electrons and electron holes for influencing the cathode electrochemical catalytic reactivity were estimated. x = 0.25 represented the better cell performance, and Ru may stabilize the LSMR grain size during electrochemical testing.     

La0.6Sr0.4Co0.2Fe0.8O3−δ cathodes infiltrated with samarium-doped cerium oxide for solid oxide fuel cells

Porous La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ (LSCF) cathodes are coated with a thin film of Sm_0.2Ce_0.8O_1.95−δ (SDC) using a one-step infiltration process. Examination of the microstructures reveals that small SDC particles are formed on the surface of LSCF grains with a relatively narrow size distribution. Impedance analysis indicates that the SDC infiltration has dramatically reduced the polarization of LSCF cathode, reaching interfacial resistances of 0.074 and 0.44 Ω cm² at 750 °C and 650 °C, respectively, which are about half of those for LSCF cathode without infiltration of SDC. The activation energies of the SDC infiltrated LSCF cathodes are in the range of 1.42-1.55 eV, slightly lower than those for a blank LSCF cathode. The SDC infiltrated LSCF cathodes have also shown improved stability under typical SOFC operating conditions, suggesting that SDC infiltration improves not only power output but also performance stability and operational life.     

Nano-structured cathodes based on La0.6Sr0.4Co0.2Fe0.8O3−δ for solid oxide fuel cells

Lanthanum-based iron- and cobalt-containing perovskite is a promising cathode material because of its electrocatalytic activity at a relatively low operating temperature in solid oxide fuel cells (SOFCs), i.e., 700-800 °C. To enhance the electrocatalytic reduction of oxidants on La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ (LSCF), nanocrystalline LSCF materials are successfully fabricated using a complexing method with chelants and inorganic nano dispersants. When inorganic dispersants are added to the synthesis process, the surface area of the LSCF powder increases from 18 to 88 m² g⁻¹, which results in higher electrocatalytic activity of the cathode. The performance of a unit cell of a SOFC with nanocrystalline LSCF powders synthesized with nano dispersants is increased by 60%, from 0.7 to 1.2 W cm⁻².     

Optimization of BaZr0.1Ce0.7Y0.2O3−δ-based proton-conducting solid oxide fuel cells with a cobalt-free proton-blocking La0.7Sr0.3FeO3−δ-Ce0.8Sm0.2O2−δ composite cathode

BaZr_0.1Ce_0.7Y_0.2O_3−δ (BZCY)-based proton-conducting solid oxide fuel cells (H-SOFC) with a cobalt-free proton-blocking La_0.7Sr_0.3FeO_3−δ-Ce_0.8Sm_0.2O_2-δ (LSF-SDC) composite cathode were fabricated and evaluated. The effect of firing temperature of the cathode layer on the chemical compatibility, microstructure of the cathode and cathode-electrolyte interface, as well as electrochemical performance of single cells was investigated in detail. The results indicated that the cell exhibited the most desirable performance when the cathode was fired at 1000 °C; moreover, at the same firing temperature, the power performance had the least temperature dependence. With humidified hydrogen (∼2% H₂O) as the fuel and ambient air as the oxidant, the polarization resistance of the cell with LSF-SDC cathode fired at 1000 °C for 3 h was as low as 0.074 Ω cm² at 650 °C after optimizing microstructures of the anode and anode-electrolyte interface, and correspondingly the maximum power density achieved as high as 542 mW cm⁻², which was the highest power output ever reported for BZCY-based H-SOFC with a cobalt-free cathode at 650 °C.